I can't decide on what my new 6th slot should be in my HG/SS play though. My 6th slot was an Alakazam with psychic and shadow ball but i'm afraid he lost his ability to sweep. I'm also about ready to rematch the Elite 4. Should i stick with him or get a good Ghost/ Dark type?

Team:
Empoleon with flash cannon and ice beam
Meganium
Crobat
Infernape
Rhyperior